Intermolecular forces aromatic molecules

From the point of view of systems (17)-(30), these aspects have been very much neglected. Most references contain some boiling and melting points but there has been no consideration of these values from the point of view of intermolecular forces between molecules. The question of aromaticity in the mesoionic systems has been poorly studied. A number of dissociation constants for systems (28)-(30) have been reported <65JCS2778>. 

Complex formation is important in photophysics. Two terms need to be described here first, an exciplex, which is an excited state complex formed between two different kinds of molecules, one that is excited and the other that is in its grown state second, an excimer, which is similar to exciplex except that the complex is formed between like molecules. Here, we will focus on excimer complexes that form between two like polymer chains or within the same polymer chain. Such complexes are often formed between two aromatic structures. Resonance interactions between aromatic structures, such as two phenyl rings in PS, give a weak intermolecular force formed from attractions between the pi-electrons of the two aromatic entities. Excimers involving such aromatic structures give strong fluorescence. 

Boiling points and melting points are considered from the point of view of intermolecular forces between the molecules, together with solubilities and chromatographic behavior, both gas and liquid chromatography. The topic of aromaticity and stability in general is covered as befits its importance. Conformations, particularly of the cyclic non-planar compounds, are dealt with. A section on tautomerism covers both prototropic tautomerism (annular and of substituents) and ring-chain tautomerism. 

The next section deals with thermodynamic aspects. This starts with a consideration of the intermolecular forces between heterocyclic molecules and their influence on melting and boiling points, solubilities, and chromatographic properties. This is followed by a section on stability and stabilization, including thermochemistry and the conformations of saturated ring systems, and a discussion of aromaticity. 

There exist several intermolecular forces between an aromatic molecule and an interacting molecule [15]. Computational methods for their evaluation will be briefly explained in this section. Dispersion, electrostatic and exchange-repulsion interactions are the major intermolecular forces when the interacting molecules are both neutral. The dispersion contribution has paramoimt importance for the attraction in the tt/tt, OH/tt, NH/tt and CH/tt interactions [8-10,16] therefore, accurate calculation of the dispersion energy is essential for the quantitative evaluation of these interactions. On the other hand, electrostatic and induction (induced polarization) interactions are the major source of the attraction in the cation/TT interaction [17]. The contribution of the dispersion interaction is relatively small in the cation/TT interactions. 

Here, however, it is possible to obtain stabilization of the low-dense lattice build-up of bulky molecules via intermolecular adhesion and orientation forces. Molecules with planar structural elements are advantageous in this respect since they are apt to support the lattice aggregate, and at the same time they are able to partition off cavities effectively. It is very convenient to use aromatic units. 

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